U.S. patent application number 12/295480 was filed with the patent office on 2009-07-09 for noise reduction circuit for canceling leakage signal.
Invention is credited to Hideki Iwaki, Naoki Komatsu, Toru Yamada.
Application Number | 20090174476 12/295480 |
Document ID | / |
Family ID | 38563395 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090174476 |
Kind Code |
A1 |
Komatsu; Naoki ; et
al. |
July 9, 2009 |
NOISE REDUCTION CIRCUIT FOR CANCELING LEAKAGE SIGNAL
Abstract
In a noise reduction circuit, a transistor circuit amplifies an
input signal and outputs an output signal with supply of power from
the DC voltage source via a power supply line circuit. The
canceling signal adding circuit acquires and attenuates a part of
the output signal, to generate a canceling signal having a phase
substantially opposite to a phase of a leakage signal leaking to
the power supply line circuit, and having an amplitude
substantially the same as an amplitude of the leakage signal.
Inventors: |
Komatsu; Naoki; (Osaka,
JP) ; Iwaki; Hideki; (Osaka, JP) ; Yamada;
Toru; (Osaka, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK L.L.P.
1030 15th Street, N.W., Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
38563395 |
Appl. No.: |
12/295480 |
Filed: |
March 28, 2007 |
PCT Filed: |
March 28, 2007 |
PCT NO: |
PCT/JP2007/056545 |
371 Date: |
January 9, 2009 |
Current U.S.
Class: |
330/149 |
Current CPC
Class: |
H01L 2223/6627 20130101;
H03F 3/245 20130101; H05K 1/0228 20130101; H03F 1/30 20130101; H05K
2201/10166 20130101; H01L 2924/19032 20130101; H03F 3/19 20130101;
H03F 1/26 20130101; H05K 1/0239 20130101; H01L 2924/19051
20130101 |
Class at
Publication: |
330/149 |
International
Class: |
H03F 1/30 20060101
H03F001/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2006 |
JP |
2006-098811 |
Claims
1-10. (canceled)
11. A noise reduction circuit comprising: a signal amplifier for
amplifying an input signal and outputting an output signal with
supply of power from a power source via a power supply line
circuit; and a signal adding circuit for acquiring and attenuating
a part of the output signal from the signal amplifier, to generate
a canceling signal having a phase substantially opposite to a phase
of a leakage signal leaking to the power supply line circuit, and
having an amplitude substantially the same as an amplitude of the
leakage signal, and for substantially canceling the leakage signal
by adding the canceling signal to the leakage signal, wherein the
power supply line circuit comprises: a low-impedance part for
substantially shorting a line of the leakage signal with a ground
to ground the leakage signal at a frequency of the leakage signal;
and a high-impedance part for setting a connection point between
the low-impedance part and the signal amplifier to a substantially
open-circuited state at the frequency of the leakage signal, and
wherein the signal adding circuit adds the canceling signal to the
leakage signal at a position which is closer to the power source
than the low-impedance part.
12. The noise reduction circuit as claimed in claim 11, wherein the
signal adding circuit is a passive circuit comprising a plurality
of passive elements.
13. The noise reduction circuit as claimed in claim 11, wherein the
signal adding circuit adds the canceling signal to the leakage
signal by using a coupler comprising one pair of transmission lines
formed in the vicinity of each other so as to be
electromagnetically coupled to each other.
14. The noise reduction circuit as claimed in claim 11, wherein the
high-impedance part is a transmission line having a length of a
quarter of a wavelength of the leakage signal, and wherein the
low-impedance part is a capacitor for passing therethrough a signal
having the frequency of the leakage signal.
15. The noise reduction circuit as claimed in claim 11, wherein the
signal adding circuit is formed on a substrate on which the signal
amplifier is mounted.
16. A signal amplifier comprising a noise reduction circuit, the
noise reduction circuit comprising: a signal amplifier for
amplifying an input signal and outputting an output signal with
supply of power from a power source via a power supply line
circuit; and a signal adding circuit for acquiring and attenuating
a part of the output signal from the signal amplifier, to generate
a canceling signal having a phase substantially opposite to a phase
of a leakage signal leaking to the power supply line circuit, and
having an amplitude substantially the same as an amplitude of the
leakage signal, and for substantially canceling the leakage signal
by adding the canceling signal to the leakage signal, wherein the
power supply line circuit comprises: a low-impedance part for
substantially shorting a line of the leakage signal with a ground
to ground the leakage signal at a frequency of the leakage signal;
and a high-impedance part for setting a connection point between
the low-impedance part and the signal amplifier to a substantially
open-circuited state at the frequency of the leakage signal,
wherein the signal adding circuit adds the canceling signal to the
leakage signal at a position which is closer to the power source
than the low-impedance part, and wherein the signal amplifier
comprises: a power terminal connected to the power supply line
circuit; and an output terminal for outputting the output
signal.
17. A wireless communication apparatus comprising a noise reduction
circuit, the noise reduction circuit comprising: a signal amplifier
for amplifying an input signal and outputting an output signal with
supply of power from a power source via a power supply line
circuit; and a signal adding circuit for acquiring and attenuating
a part of the output signal from the signal amplifier, to generate
a canceling signal having a phase substantially opposite to a phase
of a leakage signal leaking to the power supply line circuit, and
having an amplitude substantially the same as an amplitude of the
leakage signal, and for substantially canceling the leakage signal
by adding the canceling signal to the leakage signal, wherein the
power supply line circuit comprises: a low-impedance part for
substantially shorting a line of the leakage signal with a ground
to ground the leakage signal at a frequency of the leakage signal;
and a high-impedance part for setting a connection point between
the low-impedance part and the signal amplifier to a substantially
open-circuited state at the frequency of the leakage signal,
wherein the signal adding circuit adds the canceling signal to the
leakage signal at a position which is closer to the power source
than the low-impedance part, and wherein the wireless communication
apparatus comprises a transmitter for transmitting the signal
amplified by the signal amplifier.
18. A wireless communication apparatus having a receiver for
receiving a wireless signal having a predetermined frequency,
wherein the wireless communication apparatus comprises a noise
reduction circuit comprising: a signal amplifier for amplifying an
input signal and outputting an output signal with supply of power
from a power source via a power supply line circuit; and a signal
adding circuit for acquiring and attenuating a part of the output
signal from the signal amplifier, to generate a canceling signal
having a phase substantially opposite to a phase of a leakage
signal leaking to the power supply line circuit, and having an
amplitude substantially the same as an amplitude of the leakage
signal, and for substantially canceling the leakage signal by
adding the canceling signal to the leakage signal, wherein the
power supply line circuit comprises: a low-impedance part for
substantially shorting a line of the leakage signal with a ground
to ground the leakage signal at a frequency of the leakage signal;
and a high-impedance part for setting a connection point between
the low-impedance part and the signal amplifier to a substantially
open-circuited state at the frequency of the leakage signal,
wherein the signal adding circuit adds the canceling signal to the
leakage signal at a position which is closer to the power source
than the low-impedance part, wherein the high-impedance part is a
transmission line having a length of a quarter of a wavelength of
the leakage signal, wherein the low-impedance part is a capacitor
for passing therethrough a signal having the frequency of the
leakage signal, wherein the input signal is a square wave signal,
and wherein the power supply line circuit attenuates a leakage
signal which is a part of frequency components of the square wave
signal, at one of (a) a frequency of a wireless signal used in the
wireless communication apparatus, (b) an intermediate frequency
related to the wireless signal, and (c) a frequency of a baseband
signal.
19. A noise reduction method including the steps of: amplifying an
input signal and outputting an output signal by a signal amplifier
with supply of power from a power source via a power supply line
circuit; and acquiring and attenuating a part of the output signal,
to generate a canceling signal having a phase substantially
opposite to a phase of a leakage signal leaking to the power supply
line circuit, and having an amplitude substantially the same as an
amplitude of the leakage signal, wherein the power supply line
circuit comprises: a low-impedance part for substantially shorting
a line of the leakage signal with a ground to ground the leakage
signal at a frequency of the leakage signal; and a high-impedance
part for setting a connection point between the low-impedance part
and the signal amplifier to a substantially open-circuited state at
the frequency of the leakage signal, and wherein the canceling
signal is added to the leakage signal at a position which is closer
to the power source than the low-impedance part.
Description
TECHNICAL FIELD
[0001] The present invention relates to a noise reduction circuit
and method for use in wireless communication apparatuses such as
mobile telephones and wireless communication terminals, and to a
signal amplifier and a wireless communication apparatus each
employing the same noise reduction circuit.
BACKGROUND ART
[0002] Electronic devices such as mobile telephones are generally
provided with circuits each realizing various functions with an AC
(alternating current) signal with supply of a power from a DC
(direct current) power supply. Such a circuit operates under such
an assumption that a reference electric potential of a specified
portion is constant, and performs transmission, amplification and
so on of signals by adding the AC signal to the reference electric
potential. Accordingly, when an unexpected noise is superimposed on
the reference electric potential, the operations of the circuit
become unstable. Such a method (See Patent Document 1, for example)
is known for suppressing fluctuations of the reference electric
potential that a positive phase output and a negative phase output
are generated by an operational amplifier and superimposed on the
reference electric potential.
[0003] In addition, a semiconductor integrated circuit apparatus is
disclosed which can reduce crosstalk due to induction without
arranging many extra circuit elements (See Patent Document 2, for
example). In the semiconductor integrated circuit apparatus, a
plurality of parallel wiring portions are formed in a part of a
signal path so that directions of signal flowing through the
parallel wiring portions are mutually reversed. Each of the
parallel wiring portion does not include any inverters at the
halfway thereof, and the portion is a part of a real wiring, and
therefore, it is not necessary to employ any extra circuit
elements. When a signal is transmitted from one end the parallel
wiring portion, the signal is folded back partway and the signal
propagation direction is reversed at the portion. When the
directions of currents flowing through the parallel conductors are
reversed to each other, magnetic fields in different directions are
canceled due to the nature of electromagnetism, and the generation
of electromagnetic waves is suppressed. The parallel wiring
portions can ease and further suppress the crosstalk with the other
neighborhood wiring.
[0004] Patent Document 1: Japanese patent laid-open publication No.
JP-59-107615-A.
[0005] Patent Document 2: Japanese patent laid-open publication No.
JP-2003-158238-A.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] In the recent electronic devices such as portable phones,
reductions in size thereof and power consumption thereof have been
promoted, and the influence of even an extremely weak leakage
signal has become unignorable. Namely, since an internal mounting
density on a substrate is increased in a compact electronic device,
the influence of the weak leakage signal has been relatively
increased as compared with that of a circuit having a smaller
mounting density. In addition, the reduction in the power
consumption leads to a lowered application voltage of the DC
voltage source and a lowered reference electric potential with
respect to a ground, and the influence of the weak leakage signal
on the reference electric potential is relatively increased.
[0007] In particular, in the wireless communication apparatus such
as a mobile telephone, a transmission signal is amplified to a
power required for the wireless communication by an amplifier
circuit provided in an extremely small housing. However, the output
signal of the amplifier circuit is the AC signal of the largest
power in the housing, and it is concerned that the output signal
might leak to a power supply line circuit to become a interference
signal to the other devices and circuits.
[0008] In the Patent Document 1, it is possible to suppress the
fluctuations in the reference electric potential, however, it is
impossible to adopt the method of the Patent Document 1 for the
recent electronic devices in which the reduction in the power
consumption has been promoted, because the negative phase output of
the operational amplifier is utilized to suppress the fluctuations.
In addition, many parts are required such as parts for constituting
an operational amplifier and components for adjusting an output
electric potential, and therefore, it is still impossible to adopt
the method of the Patent Document 1 for the recent electronic
device in which the size reduction has been promoted.
[0009] Further, supposing the application of the method of the
Patent Document 1, it is necessary to provide an inverting
amplifier having high linearity which does not influence a signal
amplified at the previous stage of the same inverting amplifier,
and therefore, it is impractical to incorporate the method into a
circuit for the purpose of canceling the extremely weak signal.
Further, paying attention to a signal leaking to the power supply
line circuit of the amplifier, a power supply line circuit is
required for the inverting amplifier in the Patent Document 1, and
the power supply line circuit of the inverting amplifier conversely
becomes a noise source in spite of the intention of suppressing the
noise by the inverting amplifier. For the above reasons, the weak
leakage signal could not be suppressed by the methods of the above
documents.
[0010] It is an object of the present invention is to provide a
noise reduction circuit and method, and a signal amplifier and a
wireless communication apparatus each employing the same noise
reduction circuit, each capable of solving the above problems and
of reducing a noise by a simple configuration and without
preventing the reductions in size and power consumption.
Means for Solving the Problems
[0011] According to the first aspect of the present invention, a
noise reduction circuit has signal amplifying means and signal
adding means. The signal amplifying means amplifies an input signal
and outputs an output signal with supply of power from a power
source via a power supply line circuit. The signal adding means
acquires and attenuates a part of the output signal from the signal
amplifying means, to generate a canceling signal having a phase
substantially opposite to a phase of a leakage signal leaking to
the power supply line circuit, and having an amplitude
substantially the same as an amplitude of the leakage signal.
[0012] In the above mentioned noise reduction circuit, the signal
adding means is preferably a passive circuit having a plurality of
passive elements.
[0013] In addition, in the above mentioned noise reduction circuit,
the signal adding means preferably add the canceling signal to the
leakage signal by using a coupler having one pair of transmission
lines formed in the vicinity of each other so as to be
electromagnetically coupled to each other.
[0014] Further, the above mentioned noise reduction circuit
preferably has a low-impedance part for substantially shorting a
line of the leakage signal with a ground to ground the leakage
signal at a frequency of the leakage signal, and a high-impedance
part for setting a connection point between the low-impedance part
and the signal amplifying means to a substantially open-circuited
state at the frequency of the leakage signal. In this case, the
signal adding means adds the leakage signal to the leakage signal
at a position which is closer to the power source than the
low-impedance part.
[0015] In this case, the high-impedance part is preferably a
transmission line having a length of a quarter of a wavelength of
the leakage signal, and the low-impedance part is a capacitor for
passing therethrough a signal having the frequency of the leakage
signal.
[0016] Further, in the above mentioned noise reduction circuit, the
signal adding means is preferably formed on a substrate on which
the signal amplifying means is mounted.
[0017] According to the second aspect of the present invention, a
signal amplifier have the above-mentioned noise reduction circuit,
and the signal amplifier has a power terminal connected to the
power supply line circuit, and an output terminal for outputting
the output signal.
[0018] According to the third aspect of the present invention, a
wireless communication apparatus has the above-mentioned noise
reduction circuit, and the wireless communication apparatus has
transmitter means for transmitting the signal amplified by the
signal amplifying means.
[0019] According to the fourth aspect of the present invention, in
a wireless communication apparatus having receiver means for
receiving a wireless signal having a predetermined frequency, the
wireless communication apparatus has the above-mentioned noise
reduction circuit, the input signal is a square wave signal, and
the power supply line circuit attenuates a leakage signal which is
a part of frequency components of the square wave signal, at one of
(a) a frequency of a wireless signal used in the wireless
communication apparatus, (b) an intermediate frequency related to
the wireless signal, and (c) a frequency of a baseband signal.
[0020] According to the fifth aspect of the present invention, a
noise reduction method includes the steps of amplifying an input
signal and outputting an output signal with supply of power from a
power source via a power supply line circuit, and acquiring and
attenuating a part of the output signal, to generate a canceling
signal having a phase substantially opposite to a phase of a
leakage signal leaking to the power supply line circuit, and having
an amplitude substantially the same as an amplitude of the leakage
signal.
EFFECTS OF THE INVENTION
[0021] According to the noise reduction circuit and method of the
present invention, by amplifying an input signal and outputting an
output signal with supply of power from a power source via a power
supply line circuit, and acquiring and attenuating a part of the
output signal, a canceling signal is generated that has a phase
substantially opposite to a phase of a leakage signal and has an
amplitude substantially the same as an amplitude of the leakage
signal. In this case, the leaking signal leaks to the power supply
line circuit. This leads to a remarkably and effectively reduced
noise by a simple configuration and without preventing the
reductions in size and power consumption.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a block diagram showing a configuration of a
wireless communication circuit of a mobile telephone according to a
first preferred embodiment of the present invention;
[0023] FIG. 2 is a block diagram showing a detailed configuration
of a noise reduction circuit 18 of FIG. 1;
[0024] FIG. 3 is a block diagram showing a detailed configuration
of a noise reduction circuit 18a according to a second preferred
embodiment of the present invention;
[0025] FIG. 4 is a block diagram showing a detailed configuration
of a noise reduction circuit 18b according to a third preferred
embodiment of the present invention;
[0026] FIG. 5 is a block diagram showing a detailed configuration
of a noise reduction circuit 18c according to a fourth preferred
embodiment of the present invention;
[0027] FIG. 6 is a circuit diagram showing a detailed configuration
of one example of transmission lines 28c and 29d for phase
adjustment of FIG. 4;
[0028] FIG. 7 is a plan view showing a first application example
when the noise reduction circuit 18c of FIG. 4 is applied to a
printed circuit board 120;
[0029] FIG. 8 is a plan view showing a second application example
when the noise reduction circuit 18c of FIG. 4 is applied to a
signal amplifier integrated circuit (referred to as a signal
amplifier IC hereinafter) 125;
[0030] FIG. 9 is a longitudinal sectional view showing an
implemental example of FIG. 7 when a coupler 28A of FIG. 4 is
applied to the printed circuit board 120;
[0031] FIG. 10 is a longitudinal sectional view showing a first
modified preferred embodiment when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120;
[0032] FIG. 11 is a longitudinal sectional view showing a second
modified preferred embodiment when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120;
[0033] FIG. 12 is a longitudinal sectional view showing a third
modified preferred embodiment when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120;
[0034] FIG. 13 is a diagram showing a temporal waveform of a square
wave clock signal which is an input signal of the noise reduction
circuit 18 of FIG. 2;
[0035] FIG. 14 is a diagram showing a frequency characteristic of
frequency components of the square wave clock signal of FIG.
13;
[0036] FIG. 15 is a circuit diagram of a simulation circuit which
is used for a simulation conducted by the present inventors and
substantially corresponds to the noise reduction circuit 18c of
FIG. 5;
[0037] FIG. 16 is a waveform diagram of the simulation results of
FIG. 15, showing temporal waveforms of a bias voltage with or
without the noise reduction circuit for confirming a noise
reduction effect;
[0038] FIG. 17 is a graph showing a frequency characteristic of a
relative electric power of a transmission coefficient in the
transmission lines 28c and 29d for phase adjustment of FIG. 6;
and
[0039] FIG. 18 is a graph showing the frequency characteristic of
the phase of the transmission coefficient in the transmission lines
28c and 29d for phase adjustment of FIG. 6.
DESCRIPTION OF REFERENCE SYMBOLS
[0040] 10 . . . . Mobile telephone, [0041] 11 . . . . Antenna,
[0042] 12 . . . . Circulator, [0043] 13 . . . . Wireless receiver
circuit, [0044] 14 . . . . Baseband signal processing circuit,
[0045] 15 . . . . Wireless transmitter circuit, [0046] 16 . . . .
Modulator circuit, [0047] 17 . . . . Driver circuit, [0048] 18
Noise reduction circuit, [0049] 21 Transistor circuit, [0050] 22
and 23 . . . . Impedance matching circuit, [0051] 24 . . . . Power
supply line circuit, [0052] 24a . . . . Bypass capacitor, [0053]
24b . . . . Transmission line, [0054] 25 and 26 . . . . Canceling
signal adding circuit, [0055] 25a, 25b, 26a and 26b . . . .
Coupler, [0056] 25c and 26c . . . . Signal line, [0057] 27 . . . .
Capacitor, [0058] 28 and 29 . . . . Canceling signal adding
circuit, [0059] 28A, 29A and 29B . . . . Coupler, [0060] 28a, 28b,
28c, 28d, 29a, 29b, 29c, 29d and 29e: Transmission line, [0061]
28as and 28bs . . . . Strip conductor, [0062] 70 . . . .
Transmission level detector circuit, [0063] 80 . . . . Through hole
conductor, [0064] 110 . . . . Printed circuit board, [0065] 110A .
. . . Semiconductor substrate, [0066] 111 . . . . Ground conductor,
[0067] 112 . . . . Dielectric layer, [0068] 121, 122, 123 and 124 .
. . . Strip conductor, [0069] 121A, 122A, 123A and 124A . . . .
Microstrip line, [0070] 125 . . . . Signal amplifier IC, [0071]
125a . . . . Power terminal, [0072] 125b . . . . Signal output
terminal, and [0073] 126 and 127 . . . . Capacitor.
BEST MODE FOR CARRYING OUT THE INVENTION
[0074] Preferred embodiments according to the present invention
will be described below with reference to the drawings. Components
similar to each other are denoted by the same reference
numerals.
First Preferred Embodiment
[0075] FIG. 1 is a block diagram showing a configuration of a
wireless communication circuit of a mobile telephone according to
the first preferred embodiment of the present invention. FIG. 1
shows a circuit mainly for transmission and receiving of a wireless
signal. In order to transmit and receive the wireless signal, a
mobile telephone 10 is configured by including an antenna 11, a
circulator 12, a wireless receiver circuit 13, a baseband signal
processing circuit 14, and a wireless transmitter circuit 15. In
the mobile telephone 10, during the receiving, the wireless signal
received via the antenna 11 is inputted to the wireless receiver
circuit 13 via the circulator 13, and the wireless receiver circuit
13 executes processings such as frequency conversion to lower
frequency and demodulation on the received wireless signal, and
outputs the demodulated baseband signal to the baseband signal
processing circuit 14. Based on the inputted demodulated signal,
the baseband signal processing circuit 14 executes audio
outputting, data processings and so on.
[0076] The wireless transmitter circuit 100 is configured by
including a modulator circuit 16, a driver circuit 17 and a noise
reduction circuit 18, and these circuits 16, 17 and 18 are driven
by a DC voltage Vcc of a DC voltage source. In the mobile telephone
10, during the transmission, a baseband signal processed by the
baseband signal processing circuit 14 is inputted to the wireless
transmitter circuit 100. The modulator circuit 16 in the wireless
transmitter circuit 100 modulates a predetermined carrier wave
according to the inputted baseband signal to generate a modulated
wireless signal. The modulated wireless signal is outputted to the
antenna 11 via the driver circuit 17, the noise reduction circuit
18 and the circulator 12, and transmitted from the antenna 11.
[0077] As shown in FIG. 2, the noise reduction circuit 18 includes
a transistor circuit 21 which functions as a power amplifier, and a
canceling signal adding circuit 25 which reduces a noise. The
latter canceling signal adding circuit 25 acquires a part of an
output signal from the transistor circuit 21 and attenuates the
same signal. At this time, the canceling signal adding circuit 25
generates a canceling signal having a phase substantially opposite
to a phase of an output signal leaking to the power supply line
circuit of the transistor circuit 21, and having an amplitude
substantially the same as an amplitude of the leaking output
signal. Then, the canceling signal adding circuit 25 adds the
canceling signal to the output signal leaking to the power supply
line circuit. Accordingly, it is possible to suppress the noise
leaking from the noise reduction circuit 18 to the DC voltage
source side.
[0078] FIG. 2 is a block diagram showing a detailed configuration
of the noise reduction circuit 18 of FIG. 1. Referring to FIG. 2,
the noise reduction circuit 18 is configured by including a
transistor circuit 21, impedance matching circuits 22 and 23, a
power supply line circuit 24, and a canceling signal adding circuit
25. In this example, the power supply line circuit 24 includes a
bypass capacitor 24a and a transmission line 24b. In addition, the
power supply line circuit 24 is provided so as to extend in a
opposite direction to the transistor circuit 21 when seen from the
bypass capacitor 24a, and the power supply line circuit 24 is
connected to the DC voltage source Vcc via the coupler 25b of the
canceling signal adding circuit 25.
[0079] The transistor circuit 21 is an amplifier circuit that
inputs and amplifies the wireless signal outputted from the driver
circuit 17 and amplifies the signal, and the amplified transmitting
wireless signal S becomes a transmitting wireless signal
transmitted from the antenna 11. On the input side of the
transistor circuit 21, there is provided the impedance matching
circuit 22 for suppressing the loss of the wireless signal from the
driver circuit 17 by matching an output impedance of the driver
circuit 17 with an input impedance of the transistor circuit 21. On
the other hand, on the output side of the transistor circuit 21,
there is provided the impedance matching circuit 23 for suppressing
the loss of the wireless signal to be transmitted, by matching an
output impedance of the transistor circuit 21 with an output
impedance when the antenna 11 is seen via a coupler 25a. The
transistor circuit 21 and the impedance matching circuits 22 and 23
are constituted so that previously set amplification and matching
are performed within a frequency band of the transmitting wireless
signal S of the transistor circuit 21.
[0080] In addition, the power supply line circuit 24 is connected
to the transistor circuit 21, and an electric power is supplied
from the DC voltage source Vcc to the transistor circuit 21 via the
power supply line circuit 24. In order to suppress a leakage signal
from the transistor circuit 21, in the power supply line circuit
24, the transmission line 24b and the bypass capacitor 24a are
connected between the transistor circuit 21 and the DC voltage
source Vcc in this order from the transistor circuit 21. In this
case, one end of the bypass capacitor 24a is connected to the
output terminal of the transistor circuit 21, and the other end of
the bypass capacitor 24a is connected to a ground conductor (e.g.,
a ground conductor 111 of FIG. 9 described later). The bypass
capacitor 24a substantially shorts a line for a signal within a
frequency band of the transmitting wireless signal S with the
ground to ground the same signal. With this arrangement, the bypass
capacitor 24a forms a low-impedance part having a relatively low
impedance in the above frequency band.
[0081] In addition, the transmission line 24b for phase adjustment
is set so as to become a transmission line having a length of a
quarter of a wavelength of a signal in the frequency band of the
transmitting wireless signal S between the bypass capacitor 24a and
the transistor circuit 21. Accordingly, the power supply line
circuit 24 is set to a substantially open-circuited state at the
signal in the frequency band of the transmitting wireless signal S,
and forms a high-impedance part having a relatively high impedance.
Accordingly, a large part of the transmitting wireless signal S of
the transistor circuit 21 is transmitted to the impedance matching
circuit 23, and a part of the same signal is transmitted as a
leakage signal N' to the power supply line circuit 24 side.
[0082] A large part of the leakage signal N' flows to the ground
conductor by the effect of the bypass capacitor 24a, however, a
part of the leakage signal N' is transmitted to the DC voltage
source Vcc by the power supply line circuit 24. Accordingly, when
no measure is taken, an output signal (referred to as a leakage
signal N hereinafter) would be generated that leaks from the
transmission line 24b to the DC voltage source Vcc side. However,
since the reductions in size and power consumption are promoted in
the mobile telephone 10 according to the present preferred
embodiment, even a weak leakage signal N cannot be ignored.
[0083] Accordingly, in the present preferred embodiment, the
leakage signal N is canceled by the canceling signal adding circuit
25 by using a part of the transmitting wireless signal S as
follows. The canceling signal adding circuit 25 is a passive
circuit configured by including the couplers 25a and 25b, and a
signal line 25c. Referring to FIG. 2, the coupler 25a is configured
by including a transmission line between the impedance matching
circuit 23 and the antenna 11, and a further transmission line
formed in the vicinity of the above transmission line so as to be
electromagnetically coupled to the above transmission line. The
coupler 25a acquires a part of the transmitting wireless signal S
outputted from the impedance matching circuit 23, and outputs the
acquired signal to the coupler 25b via the signal line 25c.
[0084] In addition, the coupler 25b is configured by including a
transmission line provided between the bypass capacitor 24a and the
DC voltage source Vcc, and a further transmission line formed in
the vicinity of the above transmission line so as to be
electromagnetically coupled to the above transmission line. In this
case, a line length and a characteristic impedance of the power
supply line circuit 24 and the line lengths and the characteristic
impedances of the impedance matching circuit 23 and the signal line
25c of the canceling signal adding circuit 25 are previously
adjusted, so that the signal which is a part of the transmitting
wireless signal S inputted from the coupler 25a to the coupler 25b
via the signal line 25c has a phase substantially opposite to a
phase of the leakage signal N inputted from the power supply line
circuit 24 to the coupler 25b and has an amplitude substantially
the same as an amplitude of the same leakage signal N. Accordingly,
the coupler 25b of the canceling signal adding circuit 25 adds the
signal which is a part of the transmitting wireless signal S
acquired by the coupler 25a to the leakage signal N inputted from
the power supply line circuit 24 to the coupler 25b, to suppress
the leakage signal N and not to transmit the leakage signal N to
the DC voltage source Vcc side.
[0085] In addition, since a signal which is a signal source of the
leakage signal N is the transmitting wireless signal S in the
present preferred embodiment, the frequency bands of the
transmitting wireless signal S and the leakage signal N become the
same as each other. In addition, when the transmitting wireless
signal S of a certain frequency is outputted, the leakage signal N
has a frequency substantially identical to that of the transmitting
wireless signal S. Accordingly, by configuring the canceling signal
adding circuit 25 of the passive circuit which can adjust the phase
and the amplitude, it is easily possible to add a signal for
canceling the leakage signal N to the power supply line circuit
24.
[0086] Further, the transmitting wireless signal S is the signal
amplified by the transistor circuit 21, and the leakage signal N is
the signal acquired by further attenuating the leakage signal N'
leaking to the power supply line circuit 24. Accordingly, a power
of the leakage signal N is much smaller than a power of the
transmitting wireless signal S, and the canceling signal for
canceling the leakage signal N can be generated by attenuating the
power of the transmitting wireless signal S by the canceling signal
adding circuit 25. Accordingly, no additional power consumption of
an amplifier and the like is required for canceling the leakage
signal N, and the canceling of the leakage signal N can be achieved
extremely simply by the passive circuit.
[0087] In the present preferred embodiment, the transmission line
connected to the signal line 25c of the coupler 25b is formed in
the vicinity of the transmission line between the bypass capacitor
24a and the DC voltage source Vcc so that the two transmission
lines are electromagnetically coupled to each other Accordingly,
the leakage signal N can be canceled without influencing the
impedance when the power supply line circuit 24 is seen from the
output terminal of the transistor circuit 21.
[0088] For example, when the transmission line of the coupler 25b
is connected to the connection point of the bypass capacitor 24a
and the transmission line 24b, the impedance seen from the
transistor circuit 21 to the power supply line circuit 24 side
fluctuates, and it is concerned that the leakage signal N' leaking
from the transistor circuit 21 to the power supply line circuit 24
might increase. However, in the present preferred embodiment, the
coupler 25b is connected between the bypass capacitor 24a and the
DC voltage source Vcc, and there is provided the power supply line
circuit 24 including the bypass capacitor 24a and the transmission
line 24b having a line length of a quarter wavelength. Accordingly,
the leakage signal N can be further canceled while keeping the
mechanism for suppressing the leakage of the leakage signal N to
the power supply line circuit 24.
[0089] In addition, by connecting the coupler 25b between the
bypass capacitor 24a and the DC voltage source Vcc, it is possible
to determine the configurations of the couplers 25b and 25a of the
canceling signal adding circuit 25 and so on without considering
the impedance seen from the bypass capacitor 24a to the transistor
circuit 21. Namely, in the canceling signal adding circuit 25, it
becomes possible to determine the circuit configuration thereof
with paying attention only to the phase and the amplitude of the
leakage signal N, and it is possible to design the canceling signal
adding circuit 25 with an extremely high degree of freedom.
[0090] As described above, the configuration that can be designed
with a high degree of freedom is especially important in the mobile
telephone 10 whose size reduction is promoted. Namely, the
substrate and so on provided in the mobile telephone 10 are
compact, and therefore, once the parts other than the canceling
signal adding circuit 25 are determined, it is not easy to change
the arrangements and so on of the components. However, when the
design freedom of the canceling signal adding circuit 25 is high,
it is easy to constitute the canceling signal adding circuit 25
without modifying the parts other than the canceling signal adding
circuit 25. Accordingly, the present invention can be easily
applied to even compact electronic devices.
Second Preferred Embodiment
[0091] The preferred embodiment of the present invention is only
required to generate a signal for canceling the noise by acquiring
and attenuating a part of the amplified transmitting wireless
signal S, and a variety of configurations can be adopted besides
the foregoing preferred embodiment. FIG. 3 is a block diagram
showing a detailed configuration of a noise reduction circuit 18a
according to the second preferred embodiment of the present
invention. The noise reduction circuit 18a of FIG. 3 is
characterized by including a canceling signal adding circuit 26 in
stead of the canceling signal adding circuit 25 of FIG. 2 as
compared with the noise reduction circuit 18 of FIG. 2. Referring
to FIG. 3, the canceling signal adding circuit 26 is configured by
including a capacitor 27, couplers 26a and 26b, and a signal line
26c. Namely, such a configuration is adopted in which a part of the
transmitting wireless signal S is acquired by using the coupler 26a
including a transmission line to a transmission level detector
circuit 70. The configuration of FIG. 3 is described with regard to
only the points different from those of FIG. 2.
[0092] Referring to FIG. 3, the output terminal of the impedance
matching circuit 23 is connected to the transmission level detector
circuit 70 via the capacitor 27 and the coupler 26a, and a part of
the transmitting wireless signal S outputted from the impedance
matching circuit 23 is supplied to a detector provided in the
transmission level detector circuit 70, and is utilized for level
detection of the transmitting wireless signal S.
[0093] Accordingly, in the present preferred embodiment, the
canceling signal adding circuit 26 is configured by a passive
circuit. The coupler 26a of the canceling signal adding circuit 26
has the transmission line provided between the capacitor 27 and the
transmission level detector circuit 70, and a transmission line
formed in the vicinity of the above transmission line so as to be
electromagnetically coupled to the above transmission line. The
latter transmission line is connected to the coupler 26b via the
signal line 26c. Accordingly, a part of the transmitting wireless
signal S transmitted from the capacitor 27 to the transmission
level detector circuit 70 is acquired by the coupler 26a, and
thereafter, transmitted to the coupler 26b via the signal line
26c.
[0094] In addition, the coupler 26b of the canceling signal adding
circuit 26 is configured by including the transmission line
provided between the bypass capacitor 24a and the DC voltage Vcc,
and a transmission line formed in the vicinity of the above
transmission line so as to be electromagnetically coupled to the
above transmission line. The coupler 26b cancels the leakage signal
N so that the same signal is reduced, by adding a part of the
transmitting wireless signal S acquired by the coupler 26a to the
leakage signal N. Namely, the line length and the characteristic
impedance of the power supply line circuit 24 and the line lengths
and the characteristic impedances of the impedance matching circuit
23, the coupler 26a and the signal line 26c are previously
adjusted, so that a signal, which is a part of the transmitting
wireless signal S inputted from the coupler 26a to the coupler 26b
via the signal line 26c, has a phase substantially opposite to a
phase of the leakage signal N inputted from the power supply line
circuit 24 to the coupler 26b, and has an amplitude substantially
the same as an amplitude of the leakage signal N. Accordingly, the
coupler 26b of the canceling signal adding circuit 26 adds the
signal a part of the transmitting wireless signal S acquired by the
coupler 26a to the leakage signal N inputted from the power supply
line circuit 24 to the coupler 26b, and therefore, the leakage
signal N is suppressed and not transmitted to the DC voltage source
Vcc side.
[0095] Also in the present preferred embodiment, in a manner
similar to that of the above described preferred embodiment, the
canceling signal can be easily added to the leakage signal N by the
canceling signal adding circuit 26 of the passive circuit. In
addition, no additional power consumption of an amplifier and the
like is required for canceling the leakage signal N, and the
canceling of the leakage signal N can be achieved extremely simply
by the passive circuit.
[0096] Further, it is possible to further supply electric power for
canceling the leakage signal. In this case, such a mechanism is
kept for suppressing the leakage of the leakage signal N to the
power supply line circuit 24 by the power supply line circuit 24
including the bypass capacitor 24a and the transmission line 24b
having a line length of a quarter wavelength. This configuration
makes it possible to design the canceling signal adding circuit 26
with an extremely high degree of freedom. It becomes possible to
constitute the canceling signal adding circuits of a variety of
circuits due to the high design freedom of the canceling signal
adding circuit, and it becomes possible to adopt a variety of
configurations as shown in FIGS. 2 and 3.
Third Preferred Embodiment
[0097] FIG. 4 is a block diagram showing a detailed configuration
of a noise reduction circuit 18b according to the third preferred
embodiment of the present invention. The noise reduction circuit
18b of FIG. 4 is characterized by including a canceling signal
adding circuit 28 in stead of the canceling signal adding circuit
25 as compared with the noise reduction circuit 18 of FIG. 1. In
the present preferred embodiment, the canceling signal adding
circuit 28 is configured by including transmission lines 28a, 28b,
28c and 28d, and adjusts the attenuation and the phase to the
transmitting wireless signal S by changing line lengths and
distances between the lines (and preferably the characteristic
impedances in addition) of the transmission lines 28c and 28b
located between the bypass capacitor 24a and the DC voltage source
Vcc, and the transmission lines 28a and 28b located between the
impedance matching circuit 23 and the antenna 11.
[0098] Referring to FIG. 4, the connection point of the
transmission line 24b and the capacitor 24a is connected to the DC
voltage source Vcc via the transmission line 28c and the
transmission line 28b, and the output terminal of the impedance
matching circuit 23 is connected to an output terminal T2 to the
antenna 11 via the transmission line 28d and the transmission line
28a. In this case, the coupler 28A is configured by including one
pair of the transmission lines 28a and 28b formed in the vicinity
of each other so as to be electromagnetically coupled to each
other. Mainly the attenuation amount of the transmission signal S
is adjusted by the distance between the lines and the length of
paralleled lines of the transmission lines 28a and 28b. In
addition, the transmission line 28c is a transmission line for
phase adjustment, and the line length and the characteristic
impedance of the transmission line 28c are adjusted so that phases
are mutually canceled. Namely, in the present preferred embodiment,
the canceling signal adding circuit 28 is configured by using the
transmission lines 28a and 28d located between the impedance
matching circuit 23 and the antenna 11 together with the impedance
matching circuit 23 and the transmission lines 28b and 28c, without
providing an independent circuit for acquiring a part of the
transmitting wireless signal S.
[0099] In the canceling signal adding circuit 28 configured as
above, the leakage signal N is canceled by a part of the
transmitting wireless signal S, and not transmitted to the DC
voltage source Vcc side. In addition, in a manner similar to the
above described preferred embodiments, a signal for canceling the
leakage signal N can be easily added to the transmission line 28b
on the power supply line circuit 24 side by the passive circuit. In
addition, no additional power consumption of an amplifier and the
like is required for canceling the leakage signal N, and the
canceling of the leakage signal N can be achieved extremely simply
by the passive circuit. Further, it becomes possible to supply a
power for canceling the leakage signal N by using a part of the
transmitting wireless signal S. In this case, such a mechanism is
kept for suppressing the power of the leakage signal N generated by
the transmitting wireless signal S leaking to the power supply line
circuit 24 by the power supply line circuit 24. With this
arrangement, it becomes possible to design the canceling signal
adding circuit 28 with an extremely high degree of freedom.
Fourth Preferred Embodiment
[0100] FIG. 5 is a block diagram showing a detailed configuration
of a noise reduction circuit 18c according to the fourth preferred
embodiment of the present invention. The noise reduction circuit
18c of FIG. 5 is characterized by including a canceling signal
adding circuit 29 in stead of the canceling signal adding circuit
25 of FIG. 1. In the present preferred embodiment, the canceling
signal adding circuit 29 is configured by including a coupler 29A
including one pair of transmission lines 29a and 29c formed in the
vicinity of each other so as to be electromagnetically coupled to
each other, a transmission line 29d for phase adjustment, and a
coupler 29B including one pair of transmission lines 29b and 29e
formed in the vicinity of each other so as to be
electromagnetically coupled to each other. By adjusting the line
lengths and the distances between the lines (and preferably
characteristic impedances in addition) of the transmission line 29b
located between the bypass capacitor 24a and the DC voltage Vcc,
the transmission line 29a located between the impedance matching
circuit 23 and the antenna 11, and the transmission lines 29c, 29d
and 29e formed among them, the attenuation and the phase to the
transmitting wireless signal S are adjusted.
[0101] Referring to FIG. 5, by acquiring a part of the transmitting
wireless signal S by the transmission line 29c of the coupler 29A,
transmitting the partial signal to the transmission line 29e of the
coupler 29B via the transmission line 29d for phase adjustment, and
adjusting phase and amplitude thereof, the leakage signal N
transmitted via the transmission line 29b connected to the power
supply line circuit 24 is canceled by the acquired signal which is
a part of the transmitting wireless signal S and not transmitted to
the DC voltage source Vcc side.
[0102] Also in the present preferred embodiment, in a manner
similar to each of those of the above described preferred
embodiments, the signal for canceling the leakage signal N can be
easily added to the leakage signal N flowing through the power
supply line circuit 24 by the passive circuit. In addition, no
additional power consumption of an amplifier and the like is
required for canceling the leakage signal N, and the canceling of
the leakage signal N can be achieved extremely simply by the
passive circuit. Further, it is possible to further supply electric
power for canceling the leakage signal. In this case, such a
mechanism is kept for suppressing the leakage of the leakage signal
N to the power supply line circuit 24 by the power supply line
circuit 24 including the bypass capacitor 24a and the transmission
line 24b having a line length of a quarter wavelength. Further,
with this arrangement, it becomes possible to design the canceling
signal adding circuit 28 with an extremely high degree of
freedom.
[0103] FIG. 6 is a circuit diagram showing a detailed configuration
of one example of the transmission lines 28c and 29d for phase
adjustment of FIG. 4. As shown in FIG. 6, each of the transmission
lines 28c and 29d for phase adjustment is, for example, an L-type
circuit of a capacitor C1 and an inductor L1. The line length
including an amount of phase shift, the amplitude and the
characteristic impedance can be adjusted by adjusting the values of
the capacitor C1 and the inductor L1. Simulation results of the
electrical characteristics of the transmission lines 28c and 29d
for phase adjustment will be described in detail later. In
addition, the transmission line 29d may be a series circuit of the
capacitor C1 and the inductor L1 or a circuit including a
resistor.
Examples of Application to Printed Circuit Board
[0104] As can be seen, each of the preferred embodiments of the
present invention can be realized by of a variety of circuits as
described above. Each of the canceling signal adding circuits 26 to
29 may be realized by a printed circuit board (of a dielectric
substrate) 110 on which a signal amplifier IC 125 is mounted or
inside the signal amplifier IC 125. A variety of embodiments can be
adopted, and they are described in detail below.
[0105] FIG. 7 is a plan view showing a first application example in
which the noise reduction circuit 18c of FIG. 4 is applied to a
printed circuit board 120. Namely, FIG. 7 illustrates the signal
amplifier IC 125 mounted on the printed circuit board 110 and
peripheral circuits thereof. Strip conductors 121 and 122 on the
printed circuit board 110 connected to a power terminal 125a and an
output terminal 125b of the signal amplifier IC 125, respectively,
are shown in FIG. 67. In this case, a microstrip line 121A is
configured by the strip conductor 121 and a ground conductor 111
(See FIG. 9) formed on the back surface of the printed circuit
board 110, and a microstrip line 122A is configured by the strip
conductor 122 and the ground conductor 111 (See FIG. 9) formed on a
back surface of the printed circuit board 110.
[0106] The signal amplifier IC 125 of FIG. 7 is a circuit part
containing the impedance matching circuits 22 and 23 and transistor
circuit 21 provided in the noise reduction circuit 18 shown in FIG.
4. The power terminal 125a is connected between the transistor
circuit 21 and the impedance matching circuit 23, and the output
terminal 125b is connected to the output side of the impedance
matching circuit 23. Accordingly, in FIG. 7, the strip conductor
121 includes the transmission line 24b of the power supply line
circuit 24 of FIG. 4, and the strip conductor 122 corresponds to
the line conductor located between the antenna 11 and the impedance
matching circuit 23. The bypass capacitor 24a is connected to a
part of the strip conductor 121. The strip conductor 121 located
between the bypass capacitor 24a and the output terminal of the
transistor circuit 21, the wiring conductor of the signal amplifier
IC 125 and the power terminal 125a correspond to the transmission
line 24b. It is noted that another end of the bypass capacitor 24a
is connected to the ground conductor 111 via a through hole
conductor 80 filled in a through hole that penetrates the printed
circuit board 110 in the thickness direction thereof, by which
another end of the bypass capacitor 24a is grounded. Accordingly,
in the application example of FIG. 7, the coupler 28A is configured
by the strip conductors 121 and 122 that are partly formed in the
vicinity of each other so as to be electromagnetically coupled to
each other, with adjusting the line length, shape and so on of the
strip conductor 122 connected to the output terminal 125b. In the
coupler 28A, the leakage signal N transmitted via the strip
conductor 121 is canceled by the signal which is a part of the
transmitting wireless signal S transmitted though the strip
conductor 122.
[0107] According to the first application example configured as
described above, the leakage signal N can be easily canceled even
when the leakage signal N leaking from the signal amplifier IC 125
to the power supply line circuit 24 side cannot be ignored on the
printed circuit board 110 on which the arbitrary signal amplifier
IC 125 is mounted.
[0108] FIG. 8 is a plan view showing a second application example
when the noise reduction circuit 18c of FIG. 4 is applied to the
signal amplifier IC 125. As shown in FIG. 8, it is also possible to
cancel the leakage signal N in the signal amplifier IC 125 so that
the noise does not leak from the signal amplifier IC 125. Namely,
the signal amplifier IC 125 has the power terminal 125a and the
output terminal 125b, and the signal amplifier IC 125 contains a
circuit corresponding to the impedance matching circuits 22 and 23,
the transistor circuit 21, the bypass capacitor 24a, the
transmission line 24b and the canceling signal adding circuit 25
shown in the noise reduction circuit 18 of FIG. 4.
[0109] On the semiconductor substrate of the signal amplifier IC
125 of FIG. 8, a strip conductor 123 including the transmission
line 24b and the transmission line of the coupler 28A is formed
between the transistor circuit 21 and the power terminal 125a, and
a strip conductor 124 including the impedance matching circuit 23
and the transmission line of the coupler 28A is formed between the
transistor circuit 21 and the output terminal 125b. In this case, a
microstrip line 123A is configured by the strip conductor 123 and
the ground conductor (not shown, and corresponding to the ground
conductor 110 of FIG. 9, etc.) formed on a back surface of a
semiconductor substrate 110A. A microstrip line 124A is configured
by the strip conductor 124 and the ground conductor (not shown, and
corresponding to the ground conductor 110 of FIG. 9, etc.) formed
on the back surface of the semiconductor substrate 110A. One end of
the bypass capacitor 24a is connected to a part of the strip
conductor 123, and another end thereof is connected to the ground
conductor via the through hole conductor 80 filled in the through
hole that penetrates the semiconductor substrate 110A in the
thickness direction, by which another end of the bypass capacitor
24a is grounded. The impedance matching circuit 23 is configured by
a part of the strip conductor 124, and capacitors 126 and 127 each
of whose one end is grounded via the through hole conductor 80. In
this case, the canceling signal adding circuit 28 is configured by
including the impedance matching circuit 23, the strip conductor
124, the strip conductor 123, and the coupler 28A in which the two
strip conductors 123 and 124 are formed in the vicinity of each
other so as to be electromagnetically coupled to each other.
[0110] It is noted that the impedance matching circuit 22 is not
shown in FIG. 8. In this case, the leakage signal N is
substantially canceled by adding a part of the transmitting
wireless signal S to the leakage signal N by the coupler 28A, by
adjusting the line length, the shape and so on of the strip
conductor 124. According to the above configuration, the leakage
signal N can be prevented from leaking from the power terminal 125a
of the signal amplifier IC 125 to an external circuit.
[0111] In addition, the noise reduction circuit according to the
present invention may be configured by including circuit elements
different from the circuit elements described in the above
preferred embodiments. For example, the transmission line 24b may
be configured by the strip conductors 121 and 122, however, a
circuit of high impedance at the frequency of the transmitting
wireless signal S may be configured by connecting a circuit
including a choke coil and a bypass capacitor to the output
terminal of the transistor circuit 21. Further, it is possible to
configure the above passive circuit of a variety of types of
circuit elements besides the wiring patterns of the strip
conductors 121 to 124 and so on, and combinations of various types
of elements of coils, capacitors and resistors can be adopted.
[0112] Although the signal amplifier IC 125 is employed in the
application examples of FIGS. 7 and 8, the present invention is not
limited to this, and a signal amplifier may be configured by
employing a field-effect transistor without forming the signal
amplifier in the IC.
[0113] Further, the examples has been described in the foregoing
examples in which the power supply line circuit 24 and the
canceling signal adding circuit 25 are provided in the same layer
on the printed circuit board 110 or the semiconductor substrate
110A, however, these circuits may be formed in different layers.
Namely, the power supply line circuit 24 and the canceling signal
adding circuit 25 may be formed in different layers, respectively,
so long as the power can be transmitted from the strip conductor
121 or 123 provided between the impedance matching circuit 23 and
the antenna 11, to the wiring of the strip conductor or the like
provided between the bypass capacitor 24a and the DC voltage source
Vcc, by the canceling signal adding circuit 25. A variety of
configurations can be adopted. Of course, either one or both of the
power supply line circuit 24 and the canceling signal adding
circuit 25 may be formed in a plurality of layers via the through
hole conductor 80. Implemental examples of the coupler 28A are
particularly described in detail below.
[0114] FIG. 9 is a longitudinal sectional view showing an
implemental example of FIG. 7 when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120. Referring to FIG. 9,
strip conductors 28as and 28bs of one pair of transmission lines of
the coupler 28A are formed in the vicinity of each other on the
printed circuit board 110 so as to be paralleled and
electromagnetically coupled to each other. The ground conductor 111
is formed on the printed circuit board 110. The coupler 28A is
configured by the above configuration.
[0115] FIG. 10 is a longitudinal sectional view showing a first
modified preferred embodiment when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120. Referring to FIG. 10, the
strip conductors 28as and 28bs of one pair of transmission lines
are formed in the vicinity of each other so as to be
electromagnetically coupled to each other on the printed circuit
board 110, on the back surface of which the ground conductor 111 is
formed. The strip conductor 28as is formed on the front surface of
the printed circuit board 110, a dielectric layer 112 is formed on
the strip conductor 28as, and the strip conductor 28bs is formed on
the dielectric layer 112 at a position just above the strip
conductor 28as. The coupler 28A is configured by the above
configuration.
[0116] FIG. 11 is a longitudinal sectional view showing a second
modified preferred embodiment when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120. As compared with the
first modified preferred embodiment of FIG. 10, the strip conductor
28bs is formed on the dielectric layer 112 at a position shifted
from the position just above the strip conductor 28as in the second
modified preferred embodiment of FIG. 11. The coupler 28A is
configured by the above configuration.
[0117] FIG. 12 is a longitudinal sectional view showing a third
modified preferred embodiment when the coupler 28A of FIG. 4 is
applied to the printed circuit board 120. As compared with the
first modified preferred embodiment of FIG. 10, one pair of strip
conductors 28as and 28bs of the coupler 28A are formed
perpendicular to each other in the third modified preferred
embodiment of FIG. 12. The coupler 28A is configured by the above
configuration.
[0118] The two-layer structures are shown in the examples of FIGS.
9 to 12. However, the present invention is not limited to this, and
the strip conductors 28as and 28bs may be formed in arbitrary
layers of a structure of three or more layers. In addition, the
strip conductors 28as and 28bs of one pair are not required to be
parallel to each other, and are not required to have the line
widths the same as each other.
[0119] Further, such a case is examined below in which the input
signal to the noise reduction circuit 18 of FIG. 2 is a clock
signal of a square wave. FIG. 13 is a diagram showing a temporal
waveform of the clock signal of the square wave which is an input
signal of the noise reduction circuit 18 of FIG. 2. FIG. 14 is a
diagram showing a frequency characteristic of frequency components
of the clock signal of the square wave of FIG. 13. When the input
signal to the noise reduction circuit 18 of FIG. 2 is the clock
signal of the square wave as shown in FIG. 13, the clock signal
includes higher harmonic components and has frequency components in
a relatively wide frequency band as shown in FIG. 14. In such a
place where the frequency band of the communication system and the
higher harmonic components of the clock signal overlap, the clock
signal possibly exerts influences of interference or the like on
the circuit (particularly the receiver circuit) of the
communication system in the frequency band of the wireless signal
and the frequency bands related to the frequency band of the
wireless signal, such as the frequency band of an intermediate
frequency signal of an intermediate frequency acquired after
frequency conversion to lower frequency and the frequency band of
the baseband signal. In particular, when a receiving frequency band
and the higher harmonic components of the clock signal overlap, it
becomes impossible to correctly restore a signal having a weak
receiving signal power and to perform a call in the case of, for
example, a mobile telephone. All of the higher harmonic components
leak to the bias circuit side when the clock signal is amplified,
however, by using the noise reduction circuits 18, 18a, 18b and 18c
of the present preferred embodiment, such an advantageous effect
can be exhibited that the leakage signal N can be remarkably
reduced only in the frequency bands that influence the
communication system (because the power supply line circuit 24
operates as a filter circuit that removes only the predetermined
frequency bands or passes therethrough components of only the other
predetermined frequency bands as described above). In this case,
for example, the transistor circuit 21 is a circuit such as a mixer
provided in the wireless receiver circuit 13 of the wireless
communication apparatus. Further, the application examples
described above with reference to FIGS. 13 and 1 can be also
applied to, for example, a digital circuit.
Implemental Example
[0120] FIG. 15 is a circuit diagram of a simulation circuit which
is used for a simulation conducted by the present inventors and
substantially corresponds to the noise reduction circuit 18c of
FIG. 5. Referring to FIG. 15, the simulation circuit is realized by
a harmonic balance analysis method by using a simulator ADS
(Advanced Design System) produced by Agilent Technologies, and the
simulation circuit is configured by including a reference
high-frequency signal generator 30 including an internal output
resistance Rr, transmission lines 31 to 38, 39a, 39b and 40 to 43,
field-effect transistors TR1 and TR2, resistors R11 and R21,
capacitors C11 to C13 and C21, inductors L11 and L21, DC voltage
sources 51 and 52, and a load resistance R.sub.L. In this case, a
coupler 39 is configured by one pair of transmission lines 39a and
39b, and a canceling signal adding circuit 60 is configured by a
transmission line 38, a capacitor C13 and a coupler 39. In the
simulation circuit configured as above, a voltage waveform of a
bias voltage was measured at a monitoring point Tm which is a
connection point of transmission lines 42 and 43.
[0121] FIG. 16 is a waveform diagram of the simulation results of
FIG. 15, showing temporal waveforms of a bias voltage with or
without the noise reduction circuit for confirming a noise
reduction effect. As apparent from FIG. 16, it can be understood
that the leakage signal N superimposed on the bias voltage is
recognized when no noise reduction circuit 60 is provided, and the
leakage signal N is remarkably reduced when the noise reduction
circuit 60 is provided.
[0122] FIG. 17 is a graph showing a frequency characteristic of a
relative electric power of a transmission coefficient in the
transmission lines 28c and 29d for phase adjustment of FIG. 6, and
FIG. 18 is a graph showing the frequency characteristic of the
phase of the transmission coefficient in the transmission lines 28c
and 29d for phase adjustment of FIG. 6. As apparent from FIGS. 17
and 18, it can be understood that it is possible to change the
passing power and the phase shift amount depending on
frequencies.
SUMMARY OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION
[0123] According to the present invention, the noise is suppressed
by attenuating a part of an output signal amplified by the signal
amplifying means when the output signal leaks to the power supply
line circuit, and adding to the leaking output signal a signal
having a phase substantially opposite to a phase of the leaking
output signal and having an amplitude substantially the same as an
amplitude of the leaking output signal. Namely, the noise to be
suppressed is the signal which is the output signal amplified by
the signal amplifier leaking to the power supply line circuit, and
which is a weak signal. On the other hand, the signal generated by
the signal adding means is generated from a part of the output
signal amplified by the signal amplifying means, and the amplified
output signal is the signal that has a large electric power.
[0124] Accordingly, the signal adding means of the present
invention does not need any amplifier circuit in order to generate
the signal having a phase substantially opposite to a phase of the
leaking output signal and having an amplitude substantially the
same as an amplitude of the leaking output signal, and the signal
can be generated by attenuating the output signal. As a result, it
is possible to provide a circuit for canceling the output signal
leaking to the power supply line circuit without any power
consumption. In addition, no part is required for forming the
amplifier circuit or the like in order to generate the signal
having a phase substantially opposite to a phase of the leaking
output signal and having an amplitude substantially the same as an
amplitude of the leaking output signal, and the signal adding means
can be provided without preventing the size reduction of the
circuit.
[0125] In this case, the signal amplifying means is only required
to be a circuit that amplifies the input signal to acquire the
output signal, and operates to amplify the input signal by
utilizing the power supplied via the power supply line circuit. Of
course, it is possible to properly perform impedance matching or to
insert a filter in each line connected to the signal amplifying
means.
[0126] In addition, the signal leaking to the power supply line
circuit is suppressed when acquiring the output signal by
amplifying the input signal in the present invention. Accordingly,
when such an amplifying means is set to the object for application
to the present invention that a signal thereof leaks to the power
supply line, the effect is remarkably produced. An amplifying means
for a high frequency signal (e.g., signal of a frequency of equal
to or higher than 30 MHz) becomes an example of an object for
application to the present invention. Accordingly, the current
mobile telephones utilizing a band from 800 MHz to 2 GHz, the
current wireless LANs utilizing a 2 GHz band and a 5 GHz band, and
so on are preferred objects for application to the present
invention.
[0127] In addition, a part of the output signal from the signal
amplifying means is acquired by the signal adding means. Namely,
the output signal leaking from the signal amplifying means is
canceled by using the output signal amplified by the signal
amplifying means in the present invention. However, in the
amplifying means, the former signal is the output signal to be
acquired by amplification, and the latter signal is an unnecessary
noise. Accordingly, the former signal is substantially much larger
than the latter signal. Accordingly, the signal adding means can
acquire a signal that can sufficiently cancel the leaking signal
only by acquiring a part of the output signal from the signal
amplifying means.
[0128] In addition, a variety of configurations can be adopted in
order to acquire a part of the output signal, and the wirings for
electrical conduction with the wiring for transmitting the output
signal are not always essential. Namely, in such a case where the
output signal is a high frequency signal, when a circuit which is a
part of the signal adding means is wired in the vicinity of the
transmission line for transmitting the output signal, the output
signal leaks to the circuit which is a part of the signal adding
means. Accordingly, such a configuration may be adopted in which a
part of the output signal is acquired by a wiring whose electrical
conduction to the output line of the signal amplifying means is not
established. According to this configuration, a signal for
canceling the output signal leaking to the power supply line
circuit can be generated without excessively preventing the output
power of the signal amplifying means.
[0129] In addition, the signal adding means is only required to
attenuate the output signal from the signal amplifying means. The
signal adding means may have such a configuration in which a part
of the output signal is acquired and attenuated by the acquiring
simultaneously as described above, or such a configuration in which
a part of the output signal is acquired and the acquired signal
whose electric power is attenuated is further attenuated. Since the
signal attenuation as described above can be performed without any
supply of power from the power source, the attenuation can be
achieved with an extremely simple configuration.
[0130] Further, the signal generated by the signal adding means is
only required to have a phase substantially opposite to a phase of
the output signal leaking to the power supply line circuit and have
an amplitude substantially the same as an amplitude of the output
leaking signal. Namely, it is only required that the signal for
canceling the output signal leaking to the power supply line
circuit can be generated. Of course, a signal having a phase
correctly opposite to the phase of the output signal leaking to the
power supply line circuit and having an amplitude correctly the
same as the amplitude of the output leaking signal can cancel the
output leaking signal. However, when it is difficult to correctly
specify the phase and the amplitude of the leaking signal, it is
only required that the leaking signal can at least be at least
attenuated by adding a signal in the signal adding means.
[0131] In this sense, it is only required that a signal having a
phase substantially opposite to the phase the output signal leaking
to the power supply line circuit and having an amplitude
substantially the same as the amplitude of the output leaking
signal can be generated in the signal adding means. For example, it
is proper to provide such a configuration that the signal having a
phase substantially opposite to the phase the output signal leaking
to the power supply line circuit and having an amplitude
substantially the same as the amplitude of the output leaking
signal is generated by practically selectable wirings, parts and so
on.
[0132] In addition, it is sometimes the case where the output
signal has a predetermined frequency band. Accordingly, it is
acceptable to provide a configuration such that the signal adding
means selects a signal of the frequency desired to be suppressed
most, such as a signal of the greatest amplitude or the highest
transmission efficiency within the frequency band of the output
signal leaking to the power supply line circuit, and adds a signal
having a phase substantially opposite to a phase of the selected
signal and having an amplitude substantially the same as an
amplitude of the selected signal.
[0133] In the present invention, the output signal leaking to the
power supply line circuit is a part of the signal amplified by the
signal amplifying means, and substantially coincides with a
frequency band of the amplified signal. Accordingly, by canceling
the output signal leaking to the power supply line circuit by a
part of the amplified signal, the leakage signal can be attenuated
extremely easily within the entire frequency band of the output
signal leaking to the power supply line circuit.
[0134] Further, the signal adding means in the present invention
may be configured by a passive circuit. Namely, the passive circuit
is a component of a circuit such as a resistor, a capacitor or a
coil, which has no amplification effect. Each of these components
transmits a signal with effecting attenuation and phase change on
the signal. However, since it is required to generate the signal
leaking to the power supply line circuit by attenuating a part of
the output signal having a large power in the present invention,
the signal can be easily generated by a passive circuit. In
addition, because the passive circuit is utilized, power supply
from the power source is quite unnecessary for generating the
signal. Further, since it is possible to realize the signal adding
means by the simple components, the apparatus can be easily reduced
in size.
[0135] As described above, as an example in which the signal adding
means is configured by the passive circuit, such an example may be
adopted in which the signal adding means is configured by only
wirings. Namely, it is possible to adjust the phase and the
amplitude of the output signal by adjusting the length and the
shape of the lines, the distance between lines formed in the
vicinity of each other, the length of paralleled lines and so on.
Accordingly, it is possible to provide such a configuration that
the leaking output signal is canceled, by acquiring a part of the
output signal from the signal amplifying means by the wirings, and
adding the acquired signal to the power supply line circuit.
According to this configuration, the signal adding means can be
formed extremely simply.
[0136] It is noted that the present invention may be applied to a
signal amplifying means adopting a configuration for suppressing
the output signal leaking to the power supply line circuit. Namely,
the leakage of the output signal can be suppressed by adjusting the
impedance with respect to the frequency of the output signal in the
power supply line circuit. For example, in the power supply line
circuit, a low-impedance part and a high-impedance part are formed.
In this case, the ground of the low-impedance part is substantially
shorted at a frequency of the output leaking signal, and the
high-impedance part substantially open-circuits the power supply
line circuit located between the low-impedance part and the signal
amplifying means at the frequency of the leaking output signal.
[0137] According to the above configuration, the output signal
leaking to the power supply line circuit can be suppressed by the
high-impedance part and the low-impedance part. However, the
leaking output signal cannot be completely made "0" even when such
a circuit is configured by actual circuit parts, and a part of the
power leaks to the power source side. The influence of such a
leakage cannot be ignored in the recent electronic device where
reductions in size and power consumption have been promoted.
[0138] Accordingly, when the present invention is applied to such a
configuration in which the leakage of the output signal is
suppressed by the impedances as described above in the power supply
line circuit, it is possible to suppress the leakage of the output
signal to the power supply line circuit to an extremely small
level. At this time, the signal generated by the signal adding
means is added at a position closer to the power source side than
the low-impedance part. Namely, the signal leakage is prevented by
the combination of the low-impedance part and the high-impedance
part in the power supply line circuit, and therefore, when the
signal by the signal adding means is added at the position closer
to the power source side than the low-impedance part, the signal
leaking from the low-impedance part to the power source side can be
further suppressed with maintaining the mechanism for preventing
the signal leakage by the combination of the low-impedance part and
the high-impedance part.
[0139] It is noted that the low-impedance part and the
high-impedance part only required to be configured so as to
suppress the signal leaking to the power supply line circuit by the
combination of both of them. However, when the low-impedance part
and the high-impedance part are configured by actual circuit parts
and the like, it is impossible to make the impedance by the
low-impedance part "0" and to make the impedance by the
high-impedance part infinite. In this sense, it is only required to
suppress the leaking signal by making a line for the signal at the
frequency of the output signal substantially shorted with the
ground in the low-impedance part, and substantially setting the
high-impedance part to a open-circuited state for the signal at the
frequency of the leaking output signal in the high-impedance
part.
[0140] As the above configuration, it is possible to configure the
low-impedance part by a capacitor passing therethrough a signal
having the frequency of the leaking output signal, and it is
possible to configure the low-impedance part by providing a
transmission line having a length of a quarter of a wavelength of
the output leaking signal between the low-impedance part and the
signal amplifying means. With this arrangement, the low-impedance
part and the high-impedance part can be configured by an extremely
simple circuit.
[0141] By adding the signal by the signal adding means with
maintaining the mechanism to prevent the leakage of the signal by
the combination of the low-impedance part and the high-impedance
part as described above, the design freedom of the signal adding
means can be made extremely high. Namely, when such a configuration
is adopted in which the signal is added to the power supply line
circuit of the signal amplifying means, the impedance of the power
supply line circuit when seen from the signal amplifying means
generally fluctuates, and therefore, it is necessary to provide a
design conforming to this fluctuation in the signal amplifying
means.
[0142] However, as described above, in such a configuration that
the signal generated in the signal adding means is added at a
position closer to the power source side than the low-impedance
part, the addition by the signal amplifying means is performed at a
position closer to the power source side than the low-impedance
part substantially shorted with the ground. Accordingly, the
impedance when seen from the signal amplifying means scarcely
changes. Accordingly, the circuit configuration in the signal
adding means can freely be determined, and a design of an extremely
high degree of freedom can be achieved so long as the signal is
added to the power source side than the low-impedance part.
[0143] Further, the ground is substantially short-circuited at the
frequency of the leaking output signal by the low-impedance part.
However, since the signal added by the signal adding means is
provided by acquiring and attenuating a part of the output signal,
the ground is substantially short-circuited by the low-impedance
part also at the frequency of the signal added. Accordingly, it is
possible to perform the signal canceling without leaking the signal
added by the signal adding means to the signal amplifying means
side.
[0144] Further, the noise reduction apparatus of the present
invention can be applied to various signal amplifying means. For
example, in such a case where the signal amplifying means is
provided as one part and signal adding means is formed on a
substrate, when the part is mounted on the substrate, the signal
leaking from the part can be suppressed. Accordingly, even when a
part that leaks a noise is employed, the noise can be easily
suppressed.
[0145] Further, it is also possible to provide parts that leak no
noise by the present invention. As an example for the purpose, it
is acceptable to configure a part having the signal amplifying
means and the signal adding means of the present invention and
having a power terminal connected to the power supply line circuit
and an output terminal for outputting the output signal. Namely,
the output signal leaking to the power supply line circuit is
canceled inside the part, and the output signal does not leak from
the power terminal. Accordingly, the user of the part is able to
supply the predetermined power from the power terminal and to
acquire the output signal from the output terminal without taking
the leakage signal into consideration.
[0146] Further, a wireless communication apparatus such as mobile
communication apparatus can be adopted as an example of the objects
for application to the present invention. Namely, the transmission
signal is acquired by the signal amplifying means in mobile
communication apparatus, and it is often the case where the
transmission signal consumes a large power in the apparatus. In
addition, the reductions in size and power consumption have been
promoted in recent years in mobile communication apparatus, and it
is sometimes the case where the influence of the output signal
amplified by the signal amplifying means cannot be ignored.
Accordingly, when there is configured the mobile communication
apparatus having the signal amplifying means and the signal adding
means of the present invention, it is possible to provide mobile
communication apparatus of a small size and low power consumption
without being affected by the noise.
[0147] The case where the present invention is realized as an
apparatus in the above description, however, the present invention
is also applicable to a method for providing the apparatus. Of
course, the substantial operation is similar to that of the
apparatus described above. In addition, the concept of the present
invention is not limited to this, but includes a variety of forms,
as in the case where the noise reduction device as described above
is implemented singly, the case where the present invention is
applied to a method or the case where the method is utilized as
incorporated into other apparatus.
INDUSTRIAL APPLICABILITY
[0148] As described in detail above, according to the noise
reduction circuit and method of the present invention, by
amplifying an input signal and outputting an output signal with
supply of power from a power source via a power supply line
circuit, and acquiring and attenuating a part of the output signal,
a canceling signal is generated that has a phase substantially
opposite to a phase of a leakage signal and has an amplitude
substantially the same as an amplitude of the leakage signal. In
this case, the leaking signal leaks to the power supply line
circuit. This leads to a remarkably and effectively reduced noise
by a simple configuration and without preventing the reductions in
size and power consumption.
* * * * *